<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>栅格嵌套</title>
     <!-- 引入Bootstrap的css样式 -->
     <link rel="stylesheet" href="css/bootstrap.min.css" />
     <style>
         .container{
             outline:1px solid black ;
         }
         .col-md-6{
             outline: 1px solid black;
             background: rgb(85, 81, 81);
           
         }
         .col-md-3,.col-md-9{
             outline: 1px solid black;
             background: pink;
             height: 40px;
         }
     </style>
    <!-- 引入jQuery -->
    <script type="text/javascript" src="js/jquery-3.3.1.min.js"></script>
    <script type="text/javascript" src="js/bootstrap.min.js"></script>
</head>
<body>
    <div class="container">
        <div class="row">
            <div class="col-md-3">col-md-3</div>
            <div class="col-md-9 " > Levell:col-md-9
                <!-- 内部栅格 -->
                <div class="row">
                    <div class="col-md-6">col-md-6</div>
                    <div class="col-md-6">col-md-6</div>
                </div>
            </div>
        </div>
    </div>
</body>
</html>